Cotton Response to Deep Tillage with Controlled Traffic on Clay

Abstract

Tillage recommendations for clay soils indicate that subsoiling is not beneficial. This conclusion was reached by previous researchers after evaluating crop yield response to subsoiling clay soil in the spring when the soil was wet from winter rains. This study evaluated the effects of subsoiling dry clay soil (montmorillonitic, Tunica clay) compared to the recommended practice of disk-harrow tillage. Two nitrogen levels and two population levels were also included in the randomized complete block design with four replications. Duplicate experiments were installed in irrigated and non-irrigated environments in the same field. Fall subsoiling of Tunica clay soil provided significant cotton yield improvement over recommended disk-harrow tillage for three out of four years in the nonirrigated environment. Average yield increases were 14.7 and 8.2% in the nonirrigated and irrigated environments, respectively. Soil moisture tensions provided evidence of improved storage of water in the soil profile of deep-tilled treatments. Late season nitrogen (N) applications of 25 kg ha1 generally was not beneficial. An increase in plant population from 60 to 80 k plants ha1 significantly improved cotton yield in the nonirrigated environment, but did not significantly improve yield in the irrigated environment. The benefits of subsoiling dry clay soil demonstrated by this study indicates that tillage recommendations for clay soil should include soil moisture content as a constraint.